Microfluidic Controlled Self-Assembly of Polylactide (PLA)-Based Linear and Graft Copolymers into Nanoparticles with Diverse Morphologies

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This article references 73 other publications.

1. 1

   Uhrig, D.; Mays, J. W. Synthesis of Combs, Centipedes, and Barbwires: Poly(Isoprene- Graft -Styrene) Regular Multigraft Copolymers with Trifunctional, Tetrafunctional, and Hexafunctional Branch Points. Macromolecules 2002, 35 (19), 7182– 7190,  DOI: 10.1021/ma020427l

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   1

   Synthesis of Combs, Centipedes, and Barbwires: Poly(isoprene-graft-styrene) Regular Multigraft Copolymers with Trifunctional, Tetrafunctional, and Hexafunctional Branch Points

   Uhrig, David; Mays, Jimmy W.

   Macromolecules (2002), 35 (19), 7182-7190CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)

   The synthesis of poly(isoprene-graft-styrene) copolymers with multiple, regularly spaced branch points is reported. The synthetic strategy employs classical anionic polymn. techniques and utilizes a modular approach in which polystyryllithium and α,ω-poly(1,4-)isoprenyldilithium are sequentially incorporated into chlorosilane linking centers. Previous syntheses employing this basic strategy have yielded graft copolymers with trifunctional ("combs") and tetrafunctional ("centipedes") branch points. Here we further develop and extend this methodol. to include a novel regular multi-graft material with hexafunctional branch points ("barbwires"); these materials possess polystyrene side chains of uniform length attached in clusters of four at regularly spaced points along a narrow mol. wt. distribution polyisoprene main chain. In the synthesis of barbwires, PSLi is added first to 1,6-bis(trichlorosilyl)hexane, in an incremental fashion, until 4 equiv was incorporated into the linking silane; LiPILi is next added in a slight stoichiometric excess, resulting in a condensation between macromol. dinucleophiles and dielectrophiles. Homogeneous multi-graft samples of all three architectures were synthesized, with a polydispersity index of about 1.2, through fractionation of the raw condensation products.

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2. 2

   Hadjichristidis, N.; Iatrou, H.; Pitsikalis, M.; Mays, J. Macromolecular Architectures by Living and Controlled/Living Polymerizations. Prog. Polym. Sci. 2006, 31 (12), 1068– 1132,  DOI: 10.1016/j.progpolymsci.2006.07.002

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   Macromolecular architectures by living and controlled/living polymerizations

   Hadjichristidis, Nikos; Iatrou, Hermis; Pitsikalis, Marinos; Mays, Jimmy

   Progress in Polymer Science (2006), 31 (12), 1068-1132CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)

   A review. The discovery of living anionic polymn. by Szwarc 50 years ago opened the way to the synthesis of model polymers. This ground-breaking discovery inspired many researchers to develop controlled/living routes for a plethora of monomers including those not compatible with anionic polymn. These methods and their combinations serve as an arsenal for the synthesis of well-defined polymeric materials with predetd. properties and a rich variety of applications. A few representative examples of living and controlled/living methodologies for the synthesis of polymers with different macromol. architectures are presented.

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   Oh, J. K. Polylactide (PLA)-Based Amphiphilic Block Copolymers: Synthesis, Self-Assembly, and Biomedical Applications. Soft Matter 2011, 7 (11), 5096,  DOI: 10.1039/c0sm01539c

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   Polylactide (PLA)-based amphiphilic block copolymers: synthesis, self-assembly, and biomedical applications

   Oh, Jung-Kwon

   Soft Matter (2011), 7 (11), 5096-5108CODEN: SMOABF; ISSN:1744-683X. (Royal Society of Chemistry)

   A review. Polylactide (PLA) and its copolymers are one type of hydrophobic aliph. polyester based on hydroxyalkanoic acids. They possess exceptional qualities: biocompatibility; FDA approval for clin. use; biodegradability by enzyme and hydrolysis under physiol. conditions; low immunogenicity; and good mech. properties. These crit. properties have facilitated their value as sutures, implants for bone fixation, drug delivery vehicles, and tissue engineering scaffolds in pharmaceutical and biomedical applications. However, the hydrophobicity of PLA and its copolymers remains concerns for further biol. and biomedical applications. One promising approach is to design and synthesize well-controlled PLA-based amphiphilic block copolymers (ABPs); typical hydrophilic copolymers include poly(meth)acrylates, poly(ethylene glycol), polypeptides, polysaccharides, and polyurethanes. This review summarizes recent advances in the synthesis and self-assembly of PLA-contg. ABPs and their bio-related applications including drug delivery and imaging platforms of self-assembled nanoparticles, and tissue engineering of crosslinked hydrogels.

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   Song, J.; Xu, J.; Pispas, S.; Zhang, G. One-pot synthesis of poly(l-lactide)-b-poly(methyl methacrylate) block copolymers. RSC Adv. 2015, 5 (48), 38243– 38247,  DOI: 10.1039/C4RA17202G

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   Du, J.; Armes, S. P. Patchy Multi-Compartment Micelles Are Formed by Direct Dissolution of an ABC Triblock Copolymer in Water. Soft Matter 2010, 6 (19), 4851,  DOI: 10.1039/c0sm00258e

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   Wang, X.-J.; Li, G.-W.; Mo, M.-Y.; Shi, S.-H.; Li, S.-Y.; Liu, X.-Y.; Liu, L.-T. Synthesis of Poly(3-Hexylthiophene)- Block -Poly(Phenylisocyanide) Copolymers and Their Self-Assembly in Solution. Polym. Chem. 2022, 13 (46), 6361– 6368,  DOI: 10.1039/D2PY01111E

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   Trützschler, A.; Leiske, M. N.; Strumpf, M.; Brendel, J. C.; Schubert, U. S. One-Pot Synthesis of Block Copolymers by a Combination of Living Cationic and Controlled Radical Polymerization. Macromol. Rapid Commun. 2019, 40 (1), 1800398,  DOI: 10.1002/marc.201800398

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   de Freitas, A. G. O.; Trindade, S. G.; Muraro, P. I. R.; Schmidt, V.; Satti, A. J.; Villar, M. A.; Ciolino, A. E.; Giacomelli, C. Controlled One-Pot Synthesis of Polystyrene- Block -Polycaprolactone Copolymers by Simultaneous RAFT and ROP. Macromol. Chem. Phys. 2013, 214 (20), 2336– 2344,  DOI: 10.1002/macp.201300416

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   Xu, J.; Wang, X.; Hadjichristidis, N. Diblock Dialternating Terpolymers by One-Step/One-Pot Highly Selective Organocatalytic Multimonomer Polymerization. Nat. Commun. 2021, 12 (1), 7124,  DOI: 10.1038/s41467-021-27377-3

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   Diblock dialternating terpolymers by one-step/one-pot highly selective organocatalytic multimonomer polymerization

   Xu, Jiaxi; Wang, Xin; Hadjichristidis, Nikos

   Nature Communications (2021), 12 (1), 7124CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)

   The synthesis of well-defined block copolymers from a mixt. of monomers without addnl. actions ("one-pot/one-step") is an ideal and industrially valuable method. In addn., the presence of controlled alternating sequences in one or both blocks increases the structural diversity of polymeric materials, but, at the same time, the synthetic difficulty. Here we show that the "one-pot/one-step" ring-opening terpolymn. of a mixt. of three monomers (N-sulfonyl aziridines; cyclic anhydrides and epoxides), with tert-butylimino-tris(dimethylamino)phosphorene (t-BuP1) as a catalyst, results in perfect diblock dialternating terpolymers having a sharp junction between the two blocks, with highly-controllable mol. wts. and narrow mol. wt. distributions (ETH < 1.08). The organocatalyst switches between two distinct polymn. cycles without any external stimulus, showing high monomer selectivity and kinetic control. The proposed mechanism is based on NMR, in-situ FTIR, SEC, MALDI-ToF, reactivity ratios, and kinetics studies.

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    Saeed, A. O.; Dey, S.; Howdle, S. M.; Thurecht, K. J.; Alexander, C. One-Pot Controlled Synthesis of Biodegradable and Biocompatible Co-Polymer Micelles. J. Mater. Chem. 2009, 19 (26), 4529,  DOI: 10.1039/b821736j

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    One-pot controlled synthesis of biodegradable and biocompatible co-polymer micelles

    Saeed, Aram Omer; Dey, Sabrina; Howdle, Steven M.; Thurecht, Kristofer J.; Alexander, Cameron

    Journal of Materials Chemistry (2009), 19 (26), 4529-4535CODEN: JMACEP; ISSN:0959-9428. (Royal Society of Chemistry)

    A facile route to biocompatible poly(lactic acid-co-glycolic acid)-co-poly(ethyleneglycolmethacrylate) (PLGA-PEGMA) block co-polymers is described utilizing a combination of ring-opening polymn. (ROP) and reversible addn. fragmentation transfer (RAFT) methods. A series of PLGA-PEGMA polymers varying in co-monomer content and block length were synthesized with low polydispersities. All the block co-polymers formed micelles in aq. soln. as shown by dynamic light scattering, while crit. micelle concns. were found to be in the micromolar range. The polymer micelles were able to encapsulate model drugs (carboxyfluorescein and fluorescein isothiocyanate) and selected co-polymer micelles incubated with 3T3 fibroblasts as a model cell line were rapidly taken up as indicated by fluorescence microscopy assays. The combination of the polymer chemistries opens the way to highly flexible syntheses of micellar drug carrier systems.

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11. 11

    You, Y.; Hong, C.; Wang, W.; Lu, W.; Pan, C. Preparation and Characterization of Thermally Responsive and Biodegradable Block Copolymer Comprised of PNIPAAM and PLA by Combination of ROP and RAFT Methods. Macromolecules 2004, 37 (26), 9761– 9767,  DOI: 10.1021/ma048444t

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    Preparation and Characterization of Thermally Responsive and Biodegradable Block Copolymer Comprised of PNIPAAM and PLA by Combination of ROP and RAFT Methods

    You, Yezi; Hong, Chunyan; Wang, Wenping; Lu, Weiqi; Pan, Caiyuan

    Macromolecules (2004), 37 (26), 9761-9767CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)

    A special kind of reversible addn.-fragmentation chain transfer (RAFT) agent with two ending hydroxy groups, S,S'-bis(2-hydroxyethyl-2'-butyrate) trithiocarbonate (BHBT), was successfully synthesized by using polymeric supports. BHBT can act not only as initiating centers in polymn. of lactide with tin(II) 2-ethylhexanoate catalyst but also as an efficient chain transfer agent in RAFT polymn. The thermally sensitive and biodegradable block copolymers, poly(lactide-b-N-isopropylacrylamide-b-lactide) (PLA-b-PNIPAAM-b-PLA), were successfully synthesized by ring-opening polymn. (ROP) of lactide initiated from two hydroxy groups of BHBT and then RAFT polymn. of N-isopropylacrylamide (NIPAAM) using PLA with a centered trithiocarbonate unit as RAFT agent. The results of 1H NMR and GPC analyses show that the triblock copolymer of PLA-b-PNIPAAM-b-PLA with well-defined structure and controlled mol. wt. has been prepd. by combination of ROP and RAFT methods. The aq. soln. of the micelles prepd. from block copolymers using a dialysis method showed reversible changes in optical properties:transparent below a lower crit. soln. temp. (LCST) and opaque above the LCST.

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12. 12

    Seo, M.; Murphy, C. J.; Hillmyer, M. A. One-Step Synthesis of Cross-Linked Block Polymer Precursor to a Nanoporous Thermoset. ACS Macro Lett. 2013, 2 (7), 617– 620,  DOI: 10.1021/mz400192f

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    One-Step Synthesis of Cross-Linked Block Polymer Precursor to a Nanoporous Thermoset

    Seo, Myungeun; Murphy, Christopher J.; Hillmyer, Marc A.

    ACS Macro Letters (2013), 2 (7), 617-620CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)

    Using a simultaneous block polymn./in situ crosslinking from a heterofunctional initiator approach, we produced a nanostructured and cross-linked block polymer in a single step from a ternary mixt. of monomers and used it as a precursor for a cross-linked nanoporous material. Using 2-(benzylsulfanylthiocarbonylsulfanyl)ethanol as a heterofunctional initiator, simultaneous ring-opening transesterification polymn. of D,L-lactide in the presence of tin 2-ethylhexanoate as a catalyst and reversible addn.-fragmentation chain transfer polymn. of styrene at 120 °C produced a polylactide-b-polystyrene (PLA-b-PS) block polymer. Incorporation of divinylbenzene in the polymn. mixt. allowed in situ crosslinking during the simultaneous block polymn. to result in the cross-linked block polymer precursor in one step. This material was converted into cross-linked nanoporous polymer by etching PLA in a basic soln.

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    Li, Y.; Themistou, E.; Zou, J.; Das, B. P.; Tsianou, M.; Cheng, C. Facile Synthesis and Visualization of Janus Double-Brush Copolymers. ACS Macro Lett. 2012, 1 (1), 52– 56,  DOI: 10.1021/mz200013e

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    Facile Synthesis and Visualization of Janus Double-Brush Copolymers

    Li, Yukun; Themistou, Efrosyni; Zou, Jiong; Das, Biswa P.; Tsianou, Marina; Cheng, Chong

    ACS Macro Letters (2012), 1 (1), 52-56CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)

    Well-defined double-brush copolymers with each graft site carrying a polystyrene (PSt) graft and a polylactide (PLA) graft were synthesized by simultaneous reversible addn.-fragmentation chain transfer (RAFT) and ring-opening polymn. (ROP) processes, followed by ring-opening metathesis polymn. (ROMP) "grafting through" of the resulting diblock macromonomer (MM). Their Janus-type morphologies were detected by transmission electron microscopy (TEM) imaging after thermal annealing to facilitate the intramol. self-assembly of PSt and PLA grafts. This finding provides crit. evidence to verify double-brush copolymers as Janus nanomaterials.

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    Warren, N. J.; Armes, S. P. Polymerization-Induced Self-Assembly of Block Copolymer Nano-Objects via RAFT Aqueous Dispersion Polymerization. J. Am. Chem. Soc. 2014, 136 (29), 10174– 10185,  DOI: 10.1021/ja502843f

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    Polymerization-Induced Self-Assembly of Block Copolymer Nano-objects via RAFT Aqueous Dispersion Polymerization

    Warren, Nicholas J.; Armes, Steven P.

    Journal of the American Chemical Society (2014), 136 (29), 10174-10185CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    A review. In this Perspective, we discuss the recent development of polymn.-induced self-assembly mediated by reversible addn.-fragmentation chain transfer (RAFT) aq. dispersion polymn. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke org. diblock copolymer nano-objects of controllable size, morphol., and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells.

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    Jain, S.; Bates, F. S. On the Origins of Morphological Complexity in Block Copolymer Surfactants. Science 2003, 300 (5618), 460– 464,  DOI: 10.1126/science.1082193

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    On the Origins of Morphological Complexity in Block Copolymer Surfactants

    Jain, Sumeet; Bates, Frank S.

    Science (Washington, DC, United States) (2003), 300 (5618), 460-464CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)

    Amphiphilic compds. such as lipids and surfactants are fundamental building blocks of soft matter. We describe expts. with poly(1,2-butadiene-b-ethylene oxide) (PB-PEO) diblock copolymers, which form Y-junctions and three-dimensional networks in water at wt. fractions of PEO intermediate to those assocd. with vesicle and wormlike micelle morphologies. Fragmentation of the network produces a nonergodic array of complex reticulated particles that have been imaged by cryogenic transmission electron microscopy. Data obtained with two sets of PB-PEO compds. indicate that this type of self-assembly appears above a crit. mol. wt. These block copolymers represent versatile amphiphiles, mimicking certain low mol. wt. three-component (surfactant/water/oil) microemulsions, without addn. of a sep. hydrophobe.

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    Ward, M. A.; Georgiou, T. K. Thermoresponsive Polymers for Biomedical Applications. Polymers 2011, 3 (3), 1215– 1242,  DOI: 10.3390/polym3031215

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    Thermoresponsive polymers for biomedical applications

    Ward, Mark A.; Georgiou, Theoni K.

    Polymers (Basel, Switzerland) (2011), 3 (3), 1215-1242CODEN: POLYCK; ISSN:2073-4360. (MDPI AG)

    A review. Thermoresponsive polymers are a class of "smart" materials that have the ability to respond to a change in temp.; a property that makes them useful materials in a wide range of applications and consequently attracts much scientific interest. This review focuses mainly on the studies published over the last 10 years on the synthesis and use of thermoresponsive polymers for biomedical applications including drug delivery, tissue engineering and gene delivery. A summary of the main applications is given following the different studies on thermoresponsive polymers which are categorized based on their 3-dimensional structure; hydrogels, interpenetrating networks, micelles, crosslinked micelles, polymersomes, films and particles.

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17. 17

    Gaucher, G.; Dufresne, M.-H.; Sant, V. P.; Kang, N.; Maysinger, D.; Leroux, J.-C. Block Copolymer Micelles: Preparation, Characterization and Application in Drug Delivery. J. Controlled Release 2005, 109 (1–3), 169– 188,  DOI: 10.1016/j.jconrel.2005.09.034

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    Block copolymer micelles: preparation, characterization and application in drug delivery

    Gaucher, Genevieve; Dufresne, Marie-Helene; Sant, Vinayak P.; Kang, Ning; Maysinger, Dusica; Leroux, Jean-Christophe

    Journal of Controlled Release (2005), 109 (1-3), 169-188CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)

    A review. Block copolymer micelles are generally formed by the self-assembly of either amphiphilic or oppositely charged copolymers in aq. medium. The hydrophilic and hydrophobic blocks form the corona and the core of the micelles, resp. The presence of a nonionic water-sol. shell as well as the scale (10-100 nm) of polymeric micelles are expected to restrict their uptake by the mononuclear phagocyte system and allow for passive targeting of cancerous or inflamed tissues through the enhanced permeation and retention effect. Research in the field was increasingly focused on achieving enhanced stability of the micellar assembly, prolonged circulation times and controlled release of the drug for optimal targeting. With that in mind, the authors' group has developed a range of block copolymers for various applications, including amphiphilic micelles for passive targeting of chemotherapeutic agents and environment-sensitive micelles for the oral delivery of poorly bioavailable compds. Here, the authors propose to review the innovations in block copolymer synthesis, polymeric micelle prepn. and characterization, as well as the relevance of these developments to the field of biomedical research.

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18. 18

    Ratcliffe, L. P. D.; Derry, M. J.; Ianiro, A.; Tuinier, R.; Armes, S. P. A Single Thermoresponsive Diblock Copolymer Can Form Spheres, Worms or Vesicles in Aqueous Solution. Angew. Chem., Int. Ed. 2019, 58 (52), 18964– 18970,  DOI: 10.1002/anie.201909124

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    Neal, T. J.; Parnell, A. J.; King, S. M.; Beattie, D. L.; Murray, M. W.; Williams, N. S. J.; Emmett, S. N.; Armes, S. P.; Spain, S. G.; Mykhaylyk, O. O. Control of Particle Size in the Self-Assembly of Amphiphilic Statistical Copolymers. Macromolecules 2021, 54 (3), 1425– 1440,  DOI: 10.1021/acs.macromol.0c02341

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    Control of Particle Size in the Self-Assembly of Amphiphilic Statistical Copolymers

    Neal, Thomas J.; Parnell, Andrew J.; King, Stephen M.; Beattie, Deborah L.; Murray, Martin W.; Williams, Neal S. J.; Emmett, Simon N.; Armes, Steven P.; Spain, Sebastian G.; Mykhaylyk, Oleksandr O.

    Macromolecules (Washington, DC, United States) (2021), 54 (3), 1425-1440CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)

    A range of amphiphilic statistical copolymers is synthesized where the hydrophilic component is either methacrylic acid (MAA) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the hydrophobic component comprises Me, Et, Bu, hexyl, or 2-ethylhexyl methacrylate, which provide a broad range of partition coeffs. (log P). Small-angle x-ray scattering studies confirm that these amphiphilic copolymers self-assemble to form well-defined spherical nanoparticles in an aq. soln., with more hydrophobic copolymers forming larger nanoparticles. Varying the nature of the alkyl substituent also influenced self-assembly with more hydrophobic comonomers producing larger nanoparticles at a given copolymer compn. A model based on particle surface charge d. (PSC model) is used to describe the relation between copolymer compn. and nanoparticle size. This model assumes that the hydrophilic monomer is preferentially located at the particle surface and provides a good fit to all of the exptl. data. More specifically, a linear relation is obsd. between the surface area fraction covered by the hydrophilic comonomer required to achieve stabilization and the log P value for the hydrophobic comonomer. Contrast variation small-angle neutron scattering is used to study the internal structure of these nanoparticles. This technique indicates partial phase sepn. within the nanoparticles, with about half of the available hydrophilic comonomer repeat units being located at the surface and hydrophobic comonomer-rich cores. This information enables a refined PSC model to be developed, which indicates the same relation between the surface area fraction of the hydrophilic comonomer and the log P of the hydrophobic comonomer repeat units for the anionic (MAA) and cationic (DMAEMA) comonomer systems. This study demonstrates how nanoparticle size can be readily controlled and predicted using relatively ill-defined statistical copolymers, making such systems a viable attractive alternative to diblock copolymer nanoparticles for a range of industrial applications.

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    Mai, Y.; Eisenberg, A. Self-Assembly of Block Copolymers. Chem. Soc. Rev. 2012, 41 (18), 5969,  DOI: 10.1039/c2cs35115c

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    Self-assembly of block copolymers

    Mai, Yiyong; Eisenberg, Adi

    Chemical Society Reviews (2012), 41 (18), 5969-5985CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)

    A review. Block copolymer (BCP) self-assembly has attracted considerable attention for many decades. The present tutorial review introduces the primary principles of BCP self-assembly in bulk and in soln., by describing expts., theories, accessible morphologies, etc.

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    Warren, N. J.; Rosselgong, J.; Madsen, J.; Armes, S. P. Disulfide-Functionalized Diblock Copolymer Worm Gels. Biomacromolecules 2015, 16 (8), 2514– 2521,  DOI: 10.1021/acs.biomac.5b00767

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    Disulfide-Functionalized Diblock Copolymer Worm Gels

    Warren, Nicholas J.; Rosselgong, Julien; Madsen, Jeppe; Armes, Steven P.

    Biomacromolecules (2015), 16 (8), 2514-2521CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)

    Two strategies for introducing disulfide groups at the outer surface of RAFT-synthesized poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA, or Gx-Hy for brevity) diblock copolymer worms are investigated. The first approach involved statistical copolymn. of GMA with a small amt. of bis[2-(2-methacryloyloxyethyl)ethyl] disulfide (DSDMA, or D) comonomer to afford a G54-D0.50 macromol. chain transfer agent (macro-CTA); this synthesis was conducted in relatively dil. soln. in order to ensure mainly intramol. cyclization and hence the formation of linear chains. Alternatively, bis[3-(phenylthiocarbonylthio)-3-cyanobutylcarbonylamino] disulfide (DSDB) was used to prep. a G45-S-S-G45 (or (G45-S)2) macro-CTA. A binary mixt. of a non-functionalized G55 macro-CTA was utilized with each of these two disulfide-based macro-CTAs in turn for the RAFT aq. dispersion polymn. of 2-hydroxypropyl methacrylate (HPMA). By targeting a PHPMA d.p. of 130 and systematically varying the molar ratio of the two macro-CTAs, a series of disulfide-functionalized diblock copolymer worm gels were obtained. Oscillatory rheol. studies confirmed that higher disulfide contents led to stronger gels, presumably as a result of inter-worm covalent bond formation via disulfide/thiol exchange. Using the DSDB-based macro-CTA led to the strongest worm gels, and this formulation also proved to be more effective in suppressing the thermosensitive behavior that is obsd. for the nondisulfide-functionalized control worm gel. Macroscopic pptn. occurred when the proportion of DSDB-based macro-CTA was increased to 50 mol %, whereas the DSDMA-based macro-CTA could be utilized at up to 80 mol %. The worm gel modulus could be reduced to that of a nondisulfide-contg. worm gel by reductive cleavage of the inter-worm disulfide bonds using excess tris(2-carboxyethyl)phosphine (TCEP) to yield thiol groups.

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22. 22

    Lovett, J. R.; Ratcliffe, L. P. D.; Warren, N. J.; Armes, S. P.; Smallridge, M. J.; Cracknell, R. B.; Saunders, B. R. A Robust Cross-Linking Strategy for Block Copolymer Worms Prepared via Polymerization-Induced Self-Assembly. Macromolecules 2016, 49 (8), 2928– 2941,  DOI: 10.1021/acs.macromol.6b00422

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    22

    A Robust Cross-Linking Strategy for Block Copolymer Worms Prepared via Polymerization-Induced Self-Assembly

    Lovett, J. R.; Ratcliffe, L. P. D.; Warren, N. J.; Armes, S. P.; Smallridge, M. J.; Cracknell, R. B.; Saunders, B. R.

    Macromolecules (Washington, DC, United States) (2016), 49 (8), 2928-2941CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)

    A poly(glycerol monomethacrylate) (PGMA) chain transfer agent is chain-extended by reversible addn.-fragmentation chain transfer (RAFT) statistical copolymn. of 2-hydroxypropyl methacrylate (HPMA) with glycidyl methacrylate (GlyMA) in concd. aq. soln. via polymn.-induced self-assembly (PISA). A series of five free-standing worm gels is prepd. by fixing the overall d.p. of the core-forming block at 144 while varying its GlyMA content from 0 to 20 mol %. 1H NMR kinetics indicated that GlyMA is consumed much faster than HPMA, producing a GlyMA-rich sequence close to the PGMA stabilizer block. Temp.-dependent oscillatory rheol. studies indicate that increasing the GlyMA content leads to progressively less thermoresponsive worm gels, with no degelation on cooling being obsd. for worms contg. 20 mol % GlyMA. The epoxy groups in the GlyMA residues can be ring-opened using 3-aminopropyltriethoxysilane (APTES) in order to prep. core crosslinked worms via hydrolysis-condensation with the siloxane groups and/or hydroxyl groups on the HPMA residues. Perhaps surprisingly, 1H NMR anal. indicates that the epoxy-amine reaction and the intermol. crosslinking occur on similar time scales. Crosslinking leads to stiffer worm gels that do not undergo degelation upon cooling. Dynamic light scattering studies and TEM analyses conducted on linear worms exposed to either methanol (a good solvent for both blocks) or anionic surfactant result in immediate worm dissocn. In contrast, crosslinked worms remain intact under such conditions, provided that the worm cores comprise at least 10 mol % GlyMA.

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23. 23

    An, Z.; Shi, Q.; Tang, W.; Tsung, C.-K.; Hawker, C. J.; Stucky, G. D. Facile RAFT Precipitation Polymerization for the Microwave-Assisted Synthesis of Well-Defined, Double Hydrophilic Block Copolymers and Nanostructured Hydrogels. J. Am. Chem. Soc. 2007, 129 (46), 14493– 14499,  DOI: 10.1021/ja0756974

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    23

    Facile RAFT Precipitation Polymerization for the Microwave-Assisted Synthesis of Well-Defined, Double Hydrophilic Block Copolymers and Nanostructured Hydrogels

    An, Zesheng; Shi, Qihui; Tang, Wei; Tsung, Chia-Kuang; Hawker, Craig J.; Stucky, Galen D.

    Journal of the American Chemical Society (2007), 129 (46), 14493-14499CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    Water-sol. macromol. chain transfer agents (Macro-CTAs) were developed for the microwave-assisted pptn. polymn. of N-isopropylacrylamide. Two types of Macro-CTAs, amphiphilic (Macro-CTA1) and hydrophilic (Macro-CTA2), were studied regarding their activity for the facile formation of nanoparticles and double hydrophilic block copolymers by RAFT processes. While both Macro-CTAs functioned as steric stabilization agents, the variation in their surface activity afforded different levels of control over the resulting nanoparticles in the presence of crosslinkers. The crosslinked nanoparticles produced using the amphiphilic Macro-CTA1 were less uniform than those produced using the fully hydrophilic Macro-CTA2. The nanoparticles spontaneously formed core-shell structures with surface functionalities derived from those of the Macro-CTAs. In the absence of crosslinkers, both types of Macro-CTAs showed excellent control over the RAFT pptn. polymn. process with well-defined, double hydrophilic block copolymers being obtained. The power of combining microwave irradn. with RAFT procedures was evident in the high efficiency and high solids content of the polymn. systems. In addn., the "living" nature of the nanoparticles allowed for further copolymn. leading to multiresponsive nanostructured hydrogels contg. surface functional groups, which were used for surface bioconjugation.

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24. 24

    Allen, C.; Maysinger, D.; Eisenberg, A. Nano-Engineering Block Copolymer Aggregates for Drug Delivery. Colloids Surf., B 1999, 16 (1–4), 3– 27,  DOI: 10.1016/S0927-7765(99)00058-2

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25. 25

    Reineke, T. M. Stimuli-Responsive Polymers for Biological Detection and Delivery. ACS Macro Lett. 2016, 5 (1), 14– 18,  DOI: 10.1021/acsmacrolett.5b00862

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    Stimuli-Responsive Polymers for Biological Detection and Delivery

    Reineke, Theresa M.

    ACS Macro Letters (2016), 5 (1), 14-18CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)

    A review. Responsive polymers with properties designed to interact with their surrounding environment are enabling "smart" design features for custom biomaterials. Numerous applications are being innovated, ranging from diagnostics and imaging to tissue engineering and drug delivery. Herein, I feature a collection of research articles published in ACS Macro Letters that highlight an array of innovative chem. attributes such as pH-triggered hydrolytic degrdn., redn.-based release, photomodulation, glucose responsiveness, thermal sensitivity, and membrane permeating peptides. The chem., phys., mech., and morphol. properties of polymeric structures can be custom tailored to enhance numerous features such as biol. delivery, pharmaceutical potency and safety, disease diagnosis, and antigen/biomarker detection.

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26. 26

    Rahikkala, A.; Aseyev, V.; Tenhu, H.; Kauppinen, E. I.; Raula, J. Thermoresponsive Nanoparticles of Self-Assembled Block Copolymers as Potential Carriers for Drug Delivery and Diagnostics. Biomacromolecules 2015, 16 (9), 2750– 2756,  DOI: 10.1021/acs.biomac.5b00690

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27. 27

    Marsili, L.; Dal Bo, M.; Berti, F.; Toffoli, G. Chitosan-Based Biocompatible Copolymers for Thermoresponsive Drug Delivery Systems: On the Development of a Standardization System. Pharmaceutics 2021, 13 (11), 1876,  DOI: 10.3390/pharmaceutics13111876

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28. 28

    Markvicheva, E. A.; Lozinsky, V. I.; Plieva, F. M.; Kochetkov, K. A.; Rumsh, L. D.; Zubov, V. P.; Maity, J.; Kumar, R.; Parmar, V. S.; Belokon, Y. N. Gel-Immobilized Enzymes as Promising Biocatalysts: Results from Indo-Russian Collaborative Studies. Pure Appl. Chem. 2005, 77 (1), 227– 236,  DOI: 10.1351/pac200577010227

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29. 29

    Markvicheva, E. A.; Kuptsova, S. V.; Mareeva, T. Y.; Vikhrov, A. A.; Dugina, T. N.; Strukova, S. M.; Belokon, Y. N.; Kochetkov, K. A.; Baranova, E. N.; Zubov, V. P.; Poncelet, D.; Parmar, V. S.; Kumar, R.; Rumsh, L. D. Immobilized Enzymes and Cells in Poly(N-Vinyl Caprolactam)-Based Hydrogels: Preparation, Properties, and Applications in Biotechnology and Medicine. Appl. Biochem. Biotechnol. 2000, 88 (1–3), 145– 158,  DOI: 10.1385/ABAB:88:1-3:145

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30. 30

    Galaev, I. Y.; Mattiasson, B. Affinity Thermoprecipitation of Trypsin Using Soybean Trypsin Inhibitor Conjugated with a Thermo-Reactive Polymer, Poly(N-Vinyl Caprolactam). Biotechnol. Technol. 1992, 6 (4), 353– 358,  DOI: 10.1007/BF02439325

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31. 31

    Duceppe, N.; Tabrizian, M. Advances in Using Chitosan-Based Nanoparticles for in Vitro and in Vivo Drug and Gene Delivery. Expert Opin. Drug Delivery 2010, 7 (10), 1191– 1207,  DOI: 10.1517/17425247.2010.514604

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32. 32

    Maeda, T.; Akasaki, Y.; Yamamoto, K.; Aoyagi, T. Stimuli-Responsive Coacervate Induced in Binary Functionalized Poly(N -Isopropylacrylamide) Aqueous System and Novel Method for Preparing Semi-IPN Microgel Using the Coacervate. Langmuir 2009, 25 (16), 9510– 9517,  DOI: 10.1021/la9007735

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    32

    Stimuli-Responsive Coacervate Induced in Binary Functionalized Poly(N-isopropylacrylamide) Aqueous System and Novel Method for Preparing Semi-IPN Microgel Using the Coacervate

    Maeda, Tomohiro; Akasaki, Yusuke; Yamamoto, Kazuya; Aoyagi, Takao

    Langmuir (2009), 25 (16), 9510-9517CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    A method was developed for prepn. of stimuli-responsive semi-interpenetrating polymer network (semi-IPN) hydrogel microspheres via thermoresponsive coacervation. The coacervate droplets were formed in the two-component nonionic poly(N-isopropylacrylamide-2-hydroxyisopropylacrylamide) (poly(NIPAAm-HIPAAm)) and ionic poly(NIPAAm-2-carboxyisopropylacrylamide) (poly(NIPAAm-CIPAAm)) aq. system by heating the soln. above the lower crit. soln. temp. The resulting coacervate droplets included both kinds of polymer chains. Divinylsulfone, which crosslinks the hydroxyl groups of poly(NIPAAm-HIPAAm) was added to the coacervate droplets. The stimuli-responsive semi-IPN hydrogel microspheres of poly(NIPAAm-HIPAAm) gel matrix and linear poly(NIPAAm-CIPAAm) chains were obtained, with relatively homogeneous size. The thermoresponsive coacervate droplets in the binary system allowed for prepn. of fine stimuli-responsive semi-IPN hydrogel microspheres without additives.

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    Soppimath, K. S.; Aminabhavi, T. M.; Dave, A. M.; Kumbar, S. G.; Rudzinski, W. E. Stimulus-Responsive “Smart” Hydrogels as Novel Drug Delivery Systems. Drug Dev. Ind. Pharm. 2002, 28 (8), 957– 974,  DOI: 10.1081/DDC-120006428

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    33

    Stimulus-responsive "smart" hydrogels as novel drug delivery systems

    Soppimath, K. S.; Aminabhavi, T. M.; Dave, A. M.; Kumbar, S. G.; Rudzinski, W. E.

    Drug Development and Industrial Pharmacy (2002), 28 (8), 957-974CODEN: DDIPD8; ISSN:0363-9045. (Marcel Dekker, Inc.)

    A review. Recently, there has been a great deal of research activity in the development of stimulus-responsive polymeric hydrogels. These hydrogels are responsive to external or internal stimuli and the response can be obsd. through abrupt changes in the phys. nature of the network. This property can be favorable in many drug delivery applications. The external stimuli can be temp., pH, ionic strength, ultrasonic sound, elec. current, etc. A majority of the literature related to the development of stimulus-responsive drug delivery systems deals with temp.-sensitive poly(N-iso-Pr acrylamide)(pNIPAAm) and its various derivs. However, acrylic-based pH-sensitive systems with weakly acidic/basic functional groups have also been widely studied. Quite recently, glucose-sensitive hydrogels that are responsive to glucose concn. have been developed to monitor the release of insulin. The present article provides a brief introduction and recent developments in the area of stimulus-responsive hydrogels, particularly those that respond to temp. and pH, and their applications in drug delivery.

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    Lutz, J.-F. Polymerization of Oligo(Ethylene Glycol) (Meth)Acrylates: Toward New Generations of Smart Biocompatible Materials. J. Polym. Sci., Part A: Polym. Chem. 2008, 46 (11), 3459– 3470,  DOI: 10.1002/pola.22706

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    34

    Polymerization of oligo(ethylene glycol) (meth)acrylates: toward new generations of smart biocompatible materials

    Lutz, Jean-Francois

    Journal of Polymer Science, Part A: Polymer Chemistry (2008), 46 (11), 3459-3470CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)

    A review. Monomers composed of a (meth)acrylate moiety connected to a short poly(ethylene)glycol (PEG) chain are versatile building-blocks for the prepn. of "smart" biorelevant materials. Many of these monomers are com. and can be easily polymd. by either anionic, free-radical, or controlled radical polymn. The latter approach allows synthesis of well-defined PEG-based macromol. architectures such as amphiphilic block copolymers, dense polymer brushes, or biohybrids. Furthermore, the resulting polymers exhibit fascinating soln. properties in aq. medium. Depending on the mol. structure of their monomer units, non linear PEG analogs can be either insol. in water, readily sol. up to 100°, or thermoresponsive. Thus, these polymers can be used for building a wide variety of modern materials such as biosensors, artificial tissues, smart gels for chromatog., and drug carriers.

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35. 35

    Karatza, A.; Pispas, S. Poly(Hydroxyl Propyl Methacrylate)- b -Poly(Oligo Ethylene Glycol Methacrylate) Thermoresponsive Block Copolymers by RAFT Polymerization. Macromol. Chem. Phys. 2018, 219 (12), 1800060,  DOI: 10.1002/macp.201800060

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36. 36

    Yamamoto, S.-I.; Pietrasik, J.; Matyjaszewski, K. The Effect of Structure on the Thermoresponsive Nature of Well-Defined Poly(Oligo(Ethylene Oxide) Methacrylates) Synthesized by ATRP. J. Polym. Sci., Part A: Polym. Chem. 2008, 46 (1), 194– 202,  DOI: 10.1002/pola.22371

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    36

    The effect of structure on the thermoresponsive nature of well-defined poly(oligo(ethylene oxide) methacrylates) synthesized by ATRP

    Yamamoto, Shin-Ichi; Pietrasik, Joanna; Matyjaszewski, Krzysztof

    Journal of Polymer Science, Part A: Polymer Chemistry (2007), 46 (1), 194-202CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)

    Statistical copolymers of di(ethylene glycol) Me ether methacrylate (MEO2MA) and tri(ethylene glycol) Me ether methacrylate (MEO3MA) were synthesized by atom transfer radical polymn. (ATRP) providing copolymers with controlled compn. and mol. wts. ranging from Mn = 8300-56,500 with polydispersity indexes (Mw/Mn) between 1.19 and 1.28. The lower crit. soln. temp. (LCST) of the copolymers increased with the mole fraction of MEO3MA in the copolymer over the range from 26° to 52°. The av. hydrodynamic diam., measured by dynamic light scattering, varied with temp. above the LCST. These two monomers were also block copolymd. by ATRP to form polymers with mol. wt. of Mn = 30,000 and Mw/Mn from 1.12 to 1.21. The LCST of the block copolymers shifted toward the LCST of the major segment, as compared to the value measured for the statistical copolymers at the same compn. As temp. increased, micelles, consisting of aggregated PMEO2MA cores and PMEO3MA shell, were formed. The micelles aggregated upon further heating to ppt. as larger particles.

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37. 37

    Warren, N. J.; Mykhaylyk, O. O.; Mahmood, D.; Ryan, A. J.; Armes, S. P. RAFT Aqueous Dispersion Polymerization Yields Poly(Ethylene Glycol)-Based Diblock Copolymer Nano-Objects with Predictable Single Phase Morphologies. J. Am. Chem. Soc. 2014, 136 (3), 1023– 1033,  DOI: 10.1021/ja410593n

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    37

    RAFT Aqueous Dispersion Polymerization Yields Poly(ethylene glycol)-Based Diblock Copolymer Nano-Objects with Predictable Single Phase Morphologies

    Warren, Nicholas J.; Mykhaylyk, Oleksandr O.; Mahmood, Daniel; Ryan, Anthony J.; Armes, Steven P.

    Journal of the American Chemical Society (2014), 136 (3), 1023-1033CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    A poly(ethylene glycol) (PEG) macromol. chain transfer agent (macro-CTA) is prepd. in high yield (>95%) with 97% dithiobenzoate chain-end functionality in a three-step synthesis starting from a monohydroxy PEG113 precursor. This PEG113-dithiobenzoate is then used for the reversible addn.-fragmentation chain transfer (RAFT) aq. dispersion polymn. of 2-hydroxypropyl methacrylate (HPMA). Polymns. conducted under optimized conditions at 50 °C led to high conversions as judged by 1H NMR spectroscopy and relatively low diblock copolymer polydispersities (Mw/Mn < 1.25) as judged by GPC. The latter technique also indicated good blocking efficiencies, since there was minimal PEG113 macro-CTA contamination. Systematic variation of the mean d.p. of the core-forming PHPMA block allowed PEG113-PHPMAx diblock copolymer spheres, worms, or vesicles to be prepd. at up to 17.5% wt./wt. solids, as judged by dynamic light scattering and transmission electron microscopy studies. Small-angle X-ray scattering (SAXS) anal. revealed that more exotic oligolamellar vesicles were obsd. at 20% wt./wt. solids when targeting highly asym. diblock compns. Detailed anal. of SAXS curves indicated that the mean no. of membranes per oligolamellar vesicle is approx. three. A PEG113-PHPMAx phase diagram was constructed to enable the reproducible targeting of pure phases, as opposed to mixed morphologies (e.g., spheres plus worms or worms plus vesicles). This new RAFT PISA formulation is expected to be important for the rational and efficient synthesis of a wide range of biocompatible, thermo-responsive PEGylated diblock copolymer nano-objects for various biomedical applications.

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38. 38

    Varlas, S.; Neal, T. J.; Armes, S. P. Polymerization-Induced Self-Assembly and Disassembly during the Synthesis of Thermoresponsive ABC Triblock Copolymer Nano-Objects in Aqueous Solution. Chem. Sci. 2022, 13 (24), 7295– 7303,  DOI: 10.1039/D2SC01611G

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    38

    Polymerization-induced self-assembly and disassembly during the synthesis of thermoresponsive ABC triblock copolymer nano-objects in aqueous solution

    Varlas, Spyridon; Neal, Thomas J.; Armes, Steven P.

    Chemical Science (2022), 13 (24), 7295-7303CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)

    Polymn.-induced self-assembly (PISA) has been widely utilized as a powerful methodol. for the prepn. of various self-assembled AB diblock copolymer nano-objects in aq. media. Moreover, it is well-documented that chain extension of AB diblock copolymer vesicles using a range of hydrophobic monomers via seeded RAFT aq. emulsion polymn. produces framboidal ABC triblock copolymer vesicles with adjustable surface roughness owing to microphase sepn. between the two enthalpically incompatible hydrophobic blocks located within their membranes. However, the utilization of hydrophilic monomers for the chain extension of linear diblock copolymer vesicles has yet to be thoroughly explored; this omission is addressed for aq. PISA formulations in the present study. Herein poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (G-H) vesicles were used as seeds for the RAFT aq. dispersion polymn. of oligo(ethylene glycol) Me ether methacrylate (OEGMA). Interestingly, this led to polymn.-induced disassembly (PIDA), with the initial precursor vesicles being converted into lower-order worms or spheres depending on the target mean d.p. (DP) for the corona-forming POEGMA block. Moreover, construction of a pseudo-phase diagram revealed an unexpected copolymer concn. dependence for this PIDA formulation. Previously, we reported that PHPMA-based diblock copolymer nano-objects only exhibit thermoresponsive behavior over a relatively narrow range of compns. and DPs (see Warren et al., Macromols., 2018, 51, 8357-8371). However, introduction of the POEGMA coronal block produced thermoresponsive ABC triblock nano-objects even when the precursor G-H diblock copolymer vesicles proved to be thermally unresponsive. Thus, this new approach is expected to enable the rational design of new nano-objects with tunable compn., copolymer architectures and stimulus-responsive behavior.

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    Ning, Y.; Han, L.; Derry, M. J.; Meldrum, F. C.; Armes, S. P. Model Anionic Block Copolymer Vesicles Provide Important Design Rules for Efficient Nanoparticle Occlusion within Calcite. J. Am. Chem. Soc. 2019, 141 (6), 2557– 2567,  DOI: 10.1021/jacs.8b12507

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    39

    Model Anionic Block Copolymer Vesicles Provide Important Design Rules for Efficient Nanoparticle Occlusion within Calcite

    Ning, Yin; Han, Lijuan; Derry, Matthew J.; Meldrum, Fiona C.; Armes, Steven P.

    Journal of the American Chemical Society (2019), 141 (6), 2557-2567CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    Nanoparticle occlusion within growing crystals is of considerable interest because (1) it can enhance our understanding of biomineralization and (2i) it offers a straightforward route for the prepn. of novel nanocomposites. However, robust design rules for efficient occlusion remain elusive. Herein, we report the rational synthesis of a series of silica-loaded poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(ethylene glycol dimethacrylate)-poly(methacrylic acid) tetrablock copolymer vesicles using polymn.-induced self-assembly. The overall vesicle dimensions remain essentially const. for this series; hence systematic variation of the mean d.p. (DP) of the anionic poly(methacrylic acid) steric stabilizer chains provides an unprecedented opportunity to investigate the design rules for efficient nanoparticle occlusion within host inorg. crystals such as calcite. Indeed, the stabilizer DP plays a decisive role in dictating both the extent of occlusion and the calcite crystal morphol.: sufficiently long stabilizer chains are required to achieve extents of vesicle occlusion of up to 41 vol %, but overly long stabilizer chains merely lead to significant changes in the crystal morphol., rather than promoting further occlusion. Furthermore, steric stabilizer chains comprising anionic carboxylate groups lead to superior occlusion performance compared to those composed of phosphate, sulfate, or sulfonate groups. Moreover, occluded vesicles are subjected to substantial deformation forces, as shown by the significant change in shape after their occlusion. It is also demonstrated that such vesicles can act as "Trojan horses", enabling the occlusion of non-functional silica nanoparticles within calcite. In summary, this study provides important new phys. insights regarding the efficient incorporation of guest nanoparticles within host inorg. crystals.

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    Foster, J. C.; Varlas, S.; Couturaud, B.; Jones, J. R.; Keogh, R.; Mathers, R. T.; O’Reilly, R. K. Predicting Monomers for Use in Polymerization-Induced Self-Assembly. Angew. Chem., Int. Ed. 2018, 57 (48), 15733– 15737,  DOI: 10.1002/anie.201809614

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    Predicting Monomers for Use in Polymerization-Induced Self-Assembly

    Foster, Jeffrey C.; Varlas, Spyridon; Couturaud, Benoit; Jones, Joseph R.; Keogh, Robert; Mathers, Robert T.; O'Reilly, Rachel K.

    Angewandte Chemie, International Edition (2018), 57 (48), 15733-15737CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)

    We report an in silico method to predict monomers suitable for use in polymn.-induced self-assembly (PISA). By calcg. the dependence of LogPoct /surface area (SA) on the length of the growing polymer chain, the change in hydrophobicity during polymn. was detd. This allowed for evaluation of the capability of a monomer to polymerize to form self-assembled structures during chain extension. Using this method, we identified five new monomers for use in aq. PISA via reversible addn.-fragmentation chain transfer (RAFT) polymn., and confirmed that these all successfully underwent PISA to produce nanostructures of various morphologies. The results obtained using this method correlated well with and predicted the differences in morphol. obtained from the PISA of block copolymers of similar mol. wt. but different chem. structures. Thus, we propose this method can be utilized for the discovery of new monomers for PISA and also the prediction of their self-assembly behavior.

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41. 41

    Lutz, J.-F.; Akdemir, O. ̈.; Hoth, A. Point by Point Comparison of Two Thermosensitive Polymers Exhibiting a Similar LCST: Is the Age of Poly(NIPAM) Over?. J. Am. Chem. Soc. 2006, 128 (40), 13046– 13047,  DOI: 10.1021/ja065324n

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    41

    Point by Point Comparison of Two Thermosensitive Polymers Exhibiting a Similar LCST: Is the Age of Poly(NIPAM) Over?

    Lutz, Jean-Francois; Akdemir, Oezguer; Hoth, Ann

    Journal of the American Chemical Society (2006), 128 (40), 13046-13047CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    The present Communication compares the thermosensitivity in dil. aq. solns. of well-defined copolymers composed of 95% of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and 5% of oligo(ethylene glycol) methacrylate (OEGMA, Mn=475 g·mol-1) and poly(N-isopropylacrylamide) (PNIPAM) samples having similar ds. p. and chain-ends. The thermoresponsive behavior of P(MEO2MA-co-OEGMA) was overall comparable, and in some cases, superior to PNIPAM. Hence, P(MEO2MA-co-OEGMA) copolymers can be considered as ideal structures, which combine both the properties of poly(ethylene glycol) and PNIPAM in a single macromol.

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42. 42

    Cai, T.; Marquez, M.; Hu, Z. Monodisperse Thermoresponsive Microgels of Poly(Ethylene Glycol) Analogue-Based Biopolymers. Langmuir 2007, 23 (17), 8663– 8666,  DOI: 10.1021/la700923r

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    42

    Monodisperse Thermoresponsive Microgels of Poly(ethylene glycol) Analogue-Based Biopolymers

    Cai, Tong; Marquez, Manuel; Hu, Zhibing

    Langmuir (2007), 23 (17), 8663-8666CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    Monodisperse microgels of P(MEO2MA-co-OEGMA) was synthesized by free radical polymn. Microgels with a variety of particle radii ranging from 82 to 412 nm have been obtained with different surfactant concns. The particle size distribution is extremely narrow and even better than that for PNIPAM microgels. Pure MEO2MA microgels have an LCST of about 22°. The LCSTs corresponding to the molar ratio of OEGMA to MEO2MA at 10 and 20% are 31 and 37 °C, resp. Microgels in water self-assemble into various phases, including a cryst. phase with iridescent colors, which are the result of Bragg diffraction from differently oriented cryst. planes. Considering that PEG is nontoxic and anti-immunogenic as proven by the FDA, thermoresponsive P(MEO2MA-co-OEGMA) microgels may have many exciting biomedical applications.

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43. 43

    Doncom, K. E. B.; Warren, N. J.; Armes, S. P. Polysulfobetaine-Based Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly. Polym. Chem. 2015, 6 (41), 7264– 7273,  DOI: 10.1039/C5PY00396B

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    43

    Polysulfobetaine-based diblock copolymer nano-objects via polymerization-induced self-assembly

    Doncom, Kay E. B.; Warren, Nicholas J.; Armes, Steven P.

    Polymer Chemistry (2015), 6 (41), 7264-7273CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)

    A zwitterionic polysulfobetaine-based macromol. chain transfer agent (PSBMA38) was prepd. by reversible addn.-fragmentation chain transfer (RAFT) soln. polymn. of [2-(methacryloyloxy)ethyl] dimethyl(3-sulfopropyl) ammonium hydroxide (SBMA) in an aq. soln. contg. 0.5 M NaCl at 70 °C. This PSBMA38 macro-CTA was then utilized for the RAFT aq. dispersion polymn. of a water-miscible monomer, 2-hydroxypropyl methacrylate (HPMA). The growing PHPMA block became hydrophobic in situ, leading to polymn.-induced self-assembly. Systematic variation of the mean d.p. of the PHPMA block and the copolymer concn. enabled access to pure phases of spheres, worms or vesicles, as judged by transmission electron microscopy and dynamic light scattering studies. A detailed phase diagram was constructed and the thermo-responsive behavior of selected PSBMA38-PHPMAX nanoparticles was investigated. Finally, the salt tolerance of PSBMA38-PHPMA400 vesicles was compared to that of PGMA71-PHPMA400 vesicles; the former vesicles exhibit much better colloidal stability in the presence of 1 M MgSO4.

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44. 44

    Ratcliffe, L. P. D.; Blanazs, A.; Williams, C. N.; Brown, S. L.; Armes, S. P. RAFT Polymerization of Hydroxy-Functional Methacrylic Monomers under Heterogeneous Conditions: Effect of Varying the Core-Forming Block. Polym. Chem. 2014, 5 (11), 3643– 3655,  DOI: 10.1039/C4PY00203B

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    44

    RAFT polymerization of hydroxy-functional methacrylic monomers under heterogeneous conditions: effect of varying the core-forming block

    Ratcliffe, L. P. D.; Blanazs, A.; Williams, C. N.; Brown, S. L.; Armes, S. P.

    Polymer Chemistry (2014), 5 (11), 3643-3655CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)

    Statistical copolymn. of a 1:1 molar ratio of a water-miscible monomer (2-hydroxyethyl methacrylate, HEMA) with a water-immiscible monomer (4-hydroxybutyl methacrylate, HBMA) has been conducted in water via reversible addn.-fragmentation chain transfer (RAFT) polymn. using a water-sol. poly(glycerol monomethacrylate) macromol. chain transfer agent (PGMA macro-CTA). In principle, such a hybrid formulation might be expected to be intermediate between RAFT dispersion polymn. and RAFT emulsion polymn. Under such circumstances, it is of particular interest to examine whether both monomers are actually consumed and, if so, whether their rates of reaction are comparable. Given the water-soly. of both the PGMA macro-CTA and the free radical azo initiator, it is perhaps counter-intuitive that the water-immiscible HBMA is initially consumed significantly faster than the water-miscible HEMA, as judged by 1H NMR studies of this copolymn. However, both comonomers are eventually almost fully consumed at 70 °C. A detailed phase diagram has been constructed for this RAFT formulation that enables reproducible syntheses of various pure copolymer morphologies, including spheres, worms and vesicles. It is emphasized that utilizing a 1:1 HEMA/HBMA molar ratio produces a core-forming statistical copolymer block that is isomeric with the poly(2-hydroxypropyl methacrylate) (PHPMA) core-forming block previously synthesized via RAFT aq. dispersion polymn. (see A. Blanazs et al., Macromols., 2012, 45, 5099-5107). Hence it is rather remarkable that the thermo-responsive behavior of PGMA-P(HBMA-stat-HEMA) statistical block copolymer worm gels differs qual. from that exhibited by PGMA-PHPMA diblock copolymer worm gels.

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45. 45

    Blanazs, A.; Verber, R.; Mykhaylyk, O. O.; Ryan, A. J.; Heath, J. Z.; Douglas, C. W. I.; Armes, S. P. Sterilizable Gels from Thermoresponsive Block Copolymer Worms. J. Am. Chem. Soc. 2012, 134 (23), 9741– 9748,  DOI: 10.1021/ja3024059

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    45

    Sterilizable Gels from Thermoresponsive Block Copolymer Worms

    Blanazs, Adam; Verber, Robert; Mykhaylyk, Oleksandr O.; Ryan, Anthony J.; Heath, Jason Z.; Douglas, C. W. Ian; Armes, Steven P.

    Journal of the American Chemical Society (2012), 134 (23), 9741-9748CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    Biocompatible hydrogels have many applications, ranging from contact lenses to tissue engineering scaffolds. In most cases, rigorous sterilization is essential. Herein we show that a biocompatible diblock copolymer forms wormlike micelles via polymn.-induced self-assembly in aq. soln. At a copolymer concn. of 10.0 wt./wt. %, interworm entanglements lead to the formation of a free-standing phys. hydrogel at 21 °C. Gel dissoln. occurs on cooling to 4 °C due to an unusual worm-to-sphere order-order transition, as confirmed by rheol., electron microscopy, variable temp. 1H NMR spectroscopy, and scattering studies. Moreover, this thermo-reversible behavior allows the facile prepn. of sterile gels, since ultrafiltration of the diblock copolymer nanoparticles in their low-viscosity spherical form at 4 °C efficiently removes micrometer-sized bacteria; regelation occurs at 21 °C as the copolymer chains regain their wormlike morphol. Biocompatibility tests indicate good cell viabilities for these worm gels, which suggest potential biomedical applications.

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46. 46

    Penfold, N. J. W.; Whatley, J. R.; Armes, S. P. Thermoreversible Block Copolymer Worm Gels Using Binary Mixtures of PEG Stabilizer Blocks. Macromolecules 2019, 52 (4), 1653– 1662,  DOI: 10.1021/acs.macromol.8b02491

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    46

    Thermoreversible Block Copolymer Worm Gels Using Binary Mixtures of PEG Stabilizer Blocks

    Penfold, Nicholas J. W.; Whatley, Jessica R.; Armes, Steven P.

    Macromolecules (Washington, DC, United States) (2019), 52 (4), 1653-1662CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)

    Two trithiocarbonate-based poly(ethylene glycol) (PEG) macromol. chain transfer agents (macro-CTAs) with mean ds.p. of 45 and 113 were prepd. with ≥94% chain-end functionality. Binary mixts. of these PEG-trithiocarbonate macro-CTAs were then chain-extended via reversible addn.-fragmentation chain transfer (RAFT) aq. dispersion polymn. of 2-hydroxypropyl methacrylate (HPMA). Systematic variation of the relative proportions of PEG45 and PEG113 macro-CTAs and the d.p. of the PHPMA core-forming block resulted in the formation of [x PEG45 + z PEG113] - PHPMAn block copolymer spheres, worms, or vesicles, where x and z represent the mole fractions of PEG45 and PEG113, resp. A phase diagram was constructed to establish the relationship between block copolymer compn. and nanoparticle morphol. The thermoresponsive behavior of block copolymer worms was assessed by visual inspection, dynamic light scattering (DLS), transmission electron microscopy (TEM) and temp.-dependent oscillatory rheol. Increasing the proportion of PEG45 (x = 0.00-0.40) in the stabilizer block resulted in a moderate increase in worm gel strength, but cooling resulted in irreversible degelation owing to a worm-to-sphere morphol. transition. However, the phase diagram enabled identification of a single diblock copolymer compn. that exhibited reversible degelation behavior in pure water. This formulation was then further optimized to exhibit the same rheol. behavior in a com. cell culture medium (Nutristem) by fixing the PEG mole fraction at x = 0.70 while lowering the PHPMA DP from 115 to 75. Importantly, the gel strength at physiol. temp. can be readily tuned simply by variation of the copolymer concn. In principle, this study has important implications for the preservation of human stem cells, which can enter stasis when immersed in certain worm gels [see: Canton et al. ACS Cent. Sci.2016, 2, 65-74].

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47. 47

    Albuquerque, L. J. C.; Sincari, V.; Jäger, A.; Konefał, R.; Pánek, J.; Černoch, P.; Pavlova, E.; Štěpánek, P.; Giacomelli, F. C.; Jäger, E. Microfluidic-Assisted Engineering of Quasi-Monodisperse PH-Responsive Polymersomes toward Advanced Platforms for the Intracellular Delivery of Hydrophilic Therapeutics. Langmuir 2019, 35, 9b01009,  DOI: 10.1021/acs.langmuir.9b01009

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48. 48

    Jäger, E.; Jäger, A.; Etrych, T.; Giacomelli, F. C.; Chytil, P.; Jigounov, A.; Putaux, J.-L.; Říhová, B.; Ulbrich, K.; Štěpánek, P. Self-Assembly of Biodegradable Copolyester and Reactive HPMA-Based Polymers into Nanoparticles as an Alternative Stealth Drug Delivery System. Soft Matter 2012, 8 (37), 9563,  DOI: 10.1039/c2sm26150b

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    Barz, M.; Wolf, F. K.; Canal, F.; Koynov, K.; Vicent, M. J.; Frey, H.; Zentel, R. Synthesis, Characterization and Preliminary Biological Evaluation of P(HPMA)-b-P(LLA) Copolymers: A New Type of Functional Biocompatible Block Copolymer. Macromol. Rapid Commun. 2010, 31 (17), 1492– 1500,  DOI: 10.1002/marc.201000090

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    Lukáš Petrova, S.; Vragović, M.; Pavlova, E.; Černochová, Z.; Jäger, A.; Jäger, E.; Konefał, R. Smart Poly(Lactide)-b-Poly(Triethylene Glycol Methyl Ether Methacrylate) (PLA-b-PTEGMA) Block Copolymers: One-Pot Synthesis, Temperature Behavior, and Controlled Release of Paclitaxel. Pharmaceutics 2023, 15 (4), 1191,  DOI: 10.3390/pharmaceutics15041191

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    Petrova, S. L.; Pavlova, E.; Pokorný, V.; Sincari, V. Effect of Polymer Concentration on the Morphology of the PHPMAA- g -PLA Graft Copolymer Nanoparticles Produced by Microfluidics Nanoprecipitation. Nanoscale Adv. 2024, 6 (8), 1992– 1996,  DOI: 10.1039/D3NA01038D

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    Lukáš Petrova, S.; Sincari, V.; Konefał, R.; Pavlova, E.; Lobaz, V.; Kočková, O.; Hrubý, M. One-Pot/Simultaneous Synthesis of PHPMA- G -PLA Copolymers via Metal-Free Rop/Raft Polymerization and Their Self-Assembly from Micelles to Thermoresponsive Vesicles. Macromol. Chem. Phys. 2023, 224 (23), 2300271,  DOI: 10.1002/macp.202300271

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    Uhrich, K. E.; Cannizzaro, S. M.; Langer, R. S.; Shakesheff, K. M. Polymeric Systems for Controlled Drug Release. Chem. Rev. 1999, 99 (11), 3181– 3198,  DOI: 10.1021/cr940351u

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    Polymeric Systems for Controlled Drug Release

    Uhrich, Kathryn E.; Cannizzaro, Scott M.; Langer, Robert S.; Shakesheff, Kevin M.

    Chemical Reviews (Washington, D. C.) (1999), 99 (11), 3181-3198CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)

    A review with 161 refs. Mechanisms of controlled drug release, and the uses of polymers such as polyesters, polyanhydrides, in drug release devices are discussed.

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54. 54

    Singhvi, M. S.; Zinjarde, S. S.; Gokhale, D. V. Polylactic Acid: Synthesis and Biomedical Applications. J. Appl. Microbiol. 2019, 127 (6), 1612– 1626,  DOI: 10.1111/jam.14290

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    Polylactic acid: synthesis and biomedical applications

    Singhvi, M. S.; Zinjarde, S. S.; Gokhale, D. V.

    Journal of Applied Microbiology (2019), 127 (6), 1612-1626CODEN: JAMIFK; ISSN:1364-5072. (Wiley-Blackwell)

    A review. Social and economic development has driven considerable scientific and engineering efforts on the discovery, development and utilization of polymers. Polylactic acid (PLA) is one of the most promising biopolymers as it can be produced from nontoxic renewable feedstock. PLA has emerged as an important polymeric material for biomedical applications on account of its properties such as biocompatibility, biodegradability, mech. strength and process ability. Lactic acid (LA) can be obtained by fermn. of sugars derived from renewable resources such as corn and sugarcane. PLA is thus an eco-friendly nontoxic polymer with features that permit use in the human body. Although PLA has a wide spectrum of applications, there are certain limitations such as slow degrdn. rate, hydrophobicity and low impact toughness assocd. with its use. Blending PLA with other polymers offers convenient options to improve assocd. properties or to generate novel PLA polymers/blends for target applications. A variety of PLA blends have been explored for various biomedical applications such as drug delivery, implants, sutures and tissue engineering. PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues due to their excellent biocompatibility and mech. properties. The relationship between PLA material properties, manufg. processes and development of products with desirable characteristics is described in this article. LA prodn., PLA synthesis and their applications in the biomedical field are also discussed.

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55. 55

    Jacobson, G. B.; Shinde, R.; Contag, C. H.; Zare, R. N. Sustained Release of Drugs Dispersed in Polymer Nanoparticles. Angew. Chem., Int. Ed. 2008, 47 (41), 7880– 7882,  DOI: 10.1002/anie.200802260

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    Sustained release of drugs dispersed in polymer nanoparticles

    Jacobson, Gunilla B.; Shinde, Rajesh; Contag, Christopher H.; Zare, Richard N.

    Angewandte Chemie, International Edition (2008), 47 (41), 7880-7882CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)

    Supercrit. carbon dioxide was used as an antisolvent for the formation of nanoparticles that contain luciferin, a bioactive ingredient, dispersed in poly(lactic acid) (PLA), a biodegradable polymer. These nanoparticles undergo slow and sustained drug release, which can be monitored by bioluminescence both in vitro and in vivo.

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56. 56

    Giammona, G.; Craparo, E. Biomedical Applications of Polylactide (PLA) and Its Copolymers. Molecules 2018, 23 (4), 980,  DOI: 10.3390/molecules23040980

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    Wu, Y.-L.; Wang, H.; Qiu, Y.-K.; Loh, X. J. PLA-Based Thermogel for the Sustained Delivery of Chemotherapeutics in a Mouse Model of Hepatocellular Carcinoma. RSC Adv. 2016, 6 (50), 44506– 44513,  DOI: 10.1039/C6RA08022G

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    PLA-based thermogel for the sustained delivery of chemotherapeutics in a mouse model of hepatocellular carcinoma

    Wu, Yun-Long; Wang, Han; Qiu, Ying-Kun; Loh, Xian Jun

    RSC Advances (2016), 6 (50), 44506-44513CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)

    A thermogelling poly(ester urethane) comprising poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG) and poly(lactic acid) (PLA) blocks was synthesized. Drug release studies of the thermogel were carried out using paclitaxel (PTX). The release rate of the drug can be achieved by changing the concn. of the gel, greatly prolonging the release and elimination times to afford long-term effects. The thermogels showed very low toxicity on HEK293 cells. A nude mice model of hepatocellular carcinoma was developed and intratumoral injection of drug-loaded thermogel showed that PTX-loaded thermogel effectively inhibited the growth of tumors.

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    Kramschuster, A.; Turng, L.-S. An Injection Molding Process for Manufacturing Highly Porous and Interconnected Biodegradable Polymer Matrices for Use as Tissue Engineering Scaffolds. J. Biomed. Mater. Res., Part B 2009, 92B, 366– 376,  DOI: 10.1002/jbm.b.31523

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    Xu, J.; Zhang, S.; Machado, A.; Lecommandoux, S.; Sandre, O.; Gu, F.; Colin, A. Controllable Microfluidic Production of Drug-Loaded PLGA Nanoparticles Using Partially Water-Miscible Mixed Solvent Microdroplets as a Precursor. Sci. Rep. 2017, 7 (1), 4794,  DOI: 10.1038/s41598-017-05184-5

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    Controllable Microfluidic Production of Drug-Loaded PLGA Nanoparticles Using Partially Water-Miscible Mixed Solvent Microdroplets as a Precursor

    Xu Jiang; Colin Annie; Xu Jiang; Gu Frank; Xu Jiang; Zhang Shusheng; Machado Anais; Lecommandoux Sebastien; Sandre Olivier; Colin Annie

    Scientific reports (2017), 7 (1), 4794 ISSN:.

    We present a versatile continuous microfluidic flow-focusing method for the production of Doxorubicin (DOX) or Tamoxifen (TAM)-loaded poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs). We use a partially water-miscible solvent mixture (dimethyl sulfoxide DMSO+ dichloromethane DCM) as precursor drug/polymer solution for NPs nucleation. We extrude this partially water-miscible solution into an aqueous medium and synthesized uniform PLGA NPs with higher drug loading ability and longer sustained-release ability than conventional microfluidic or batch preparation methods. The size of NPs could be precisely tuned by changing the flow rate ratios, polymer concentration, and volume ratio of DCM to DMSO (VDCM/VDMSO) in the precursor emulsion. We investigated the mechanism of the formation of NPs and the effect of VDCM/VDMSO on drug release kinetics. Our work suggests that this original, rapid, facile, efficient and low-cost method is a promising technology for high throughput NP fabrication. For the two tested drugs, one hydrophilic (Doxorubicin) the other one hydrophobic (Tamoxifen), encapsulation efficiency (EE) as high as 88% and mass loading content (LC) higher than 25% were achieved. This new process could be extended as an efficient and large scale NP production method to benefit to fields like controlled drug release and nanomedicine.

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60. 60

    Tan, Z.; Lan, W.; Liu, Q.; Wang, K.; Hussain, M.; Ren, M.; Geng, Z.; Zhang, L.; Luo, X.; Zhang, L.; Zhu, J. Kinetically Controlled Self-Assembly of Block Copolymers into Segmented Wormlike Micelles in Microfluidic Chips. Langmuir 2019, 35 (1), 141– 149,  DOI: 10.1021/acs.langmuir.8b03028

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    Ulbrich, K.; Šubr, V.; Strohalm, J.; Plocová, D.; Jelínková, M.; Říhová, B. Polymeric Drugs Based on Conjugates of Synthetic and Natural Macromolecules. J. Controlled Release 2000, 64 (1–3), 63– 79,  DOI: 10.1016/S0168-3659(99)00141-8

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    Danial, M.; Telwatte, S.; Tyssen, D.; Cosson, S.; Tachedjian, G.; Moad, G.; Postma, A. Combination Anti-HIV Therapy via Tandem Release of Prodrugs from Macromolecular Carriers. Polym. Chem. 2016, 7 (48), 7477– 7487,  DOI: 10.1039/C6PY01882C

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    Zhang, Q.; Weber, C.; Schubert, U. S.; Hoogenboom, R. Thermoresponsive Polymers with Lower Critical Solution Temperature: From Fundamental Aspects and Measuring Techniques to Recommended Turbidimetry Conditions. Mater. Horiz. 2017, 4 (2), 109– 116,  DOI: 10.1039/C7MH00016B

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    Thermoresponsive polymers with lower critical solution temperature: from fundamental aspects and measuring techniques to recommended turbidimetry conditions

    Zhang, Qilu; Weber, Christine; Schubert, Ulrich S.; Hoogenboom, Richard

    Materials Horizons (2017), 4 (2), 109-116CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)

    Thermoresponsive polymers that undergo reversible phase transition by responding to an environmental temp. change, in particular polymers showing lower crit. soln. temp. (LCST), are frequently used as smart materials that have found increasing applications. Recently, there has been a rapid growth in interest on LCST polymers and many new research groups are entering the field from a wide range of application areas. While it is great to see more researchers working on LCST polymers, the downside of this rapid growth is that the fundamentals of the LCST phase transition behavior are not always clearly known and respected. Hence, this focus article provides a systematic discussion of the key aspects of the LCST behavior of polymers starting from fundamentals of LCST behavior to practical detn. of cloud point temp. (Tcp). Finally, we offer a basic set of recommended measuring conditions for detn. of Tcp (10 mg mL-1; 0.5°C min-1; 600 nm) to facilitate the comparison of the LCST behavior and Tcp values of polymers developed and studied in different labs. around the globe, which is nowadays nearly impossible since various techniques and parameters are being utilized for the measurements. It should be noted that these recommended conditions serve as a robust tool for turbidimetry, which is one out of the many characterization techniques one should utilize to fully understand LCST behavior of polymers.

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    Halperin, A.; Kröger, M.; Winnik, F. M. Poly(N -isopropylacrylamide) Phase Diagrams: Fifty Years of Research. Angew. Chem., Int. Ed. 2015, 54 (51), 15342– 15367,  DOI: 10.1002/anie.201506663

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    Poly(N-isopropylacrylamide) Phase Diagrams: Fifty Years of Research

    Halperin, Avraham; Kroeger, Martin; Winnik, Francoise M.

    Angewandte Chemie, International Edition (2015), 54 (51), 15342-15367CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)

    A review. In 1968, Heskins and Guillet published the first systematic study of the phase diagram of poly(N-isopropylacrylamide) (PNIPAM), at the time a "young polymer" first synthesized in 1956. Since then, PNIPAM became the leading member of the growing families of thermoresponsive polymers and of stimuli-responsive, "smart" polymers in general. Its thermal response is unanimously attributed to its phase behavior. Yet, in spite of 50 years of research, a coherent quant. picture remains elusive. In this Review we survey the reported phase diagrams, discuss the differences and comment on theor. ideas regarding their possible origins. We aim to alert the PNIPAM community to open questions in this reputably mature domain.

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    Guinier, A.; Fournet, G.; Walker, C. B.; Vineyard, G. H. Small-Angle Scattering of X-Rays. Phys. Today 1956, 9 (8), 38– 39,  DOI: 10.1063/1.3060069

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    Themistou, E.; Battaglia, G.; Armes, S. P. Facile Synthesis of Thiol-Functionalized Amphiphilic Polylactide-Methacrylic Diblock Copolymers. Polym. Chem. 2014, 5 (4), 1405– 1417,  DOI: 10.1039/C3PY01446K

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    Facile synthesis of thiol-functionalized amphiphilic polylactide-methacrylic diblock copolymers

    Themistou, Efrosyni; Battaglia, Giuseppe; Armes, Steven P.

    Polymer Chemistry (2014), 5 (4), 1405-1417CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)

    Biodegradable amphiphilic diblock copolymers based on an aliph. ester block and various hydrophilic methacrylic monomers were synthesized using a novel hydroxyl-functionalized trithiocarbonate-based chain transfer agent. One protocol involved the one-pot simultaneous ring-opening polymn. (ROP) of the biodegradable monomer (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (l-lactide, LA) and reversible addn.-fragmentation chain transfer (RAFT) polymn. of 2-(dimethylamino)ethyl methacrylate (DMA) or oligo(ethylene glycol) methacrylate (OEGMA) monomer, with 4-dimethylaminopyridine being used as the ROP catalyst and 2,2'-azobis(isobutyronitrile) as the initiator for the RAFT polymn. Alternatively, a two-step protocol involving the initial polymn. of LA followed by the polymn. of DMA, glycerol monomethacrylate or 2-(methacryloyloxy)ethyl phosphorylcholine using 4,4'-azobis(4-cyanovaleric acid) as a RAFT initiator was also explored. Using a solvent switch processing step, these amphiphilic diblock copolymers self-assemble in dil. aq. soln. Their self-assembly provides various copolymer morphologies depending on the block compns., as judged by transmission electron microscopy and dynamic light scattering. Two novel disulfide-functionalized PLA-branched block copolymers were also synthesized using simultaneous ROP of LA and RAFT copolymn. of OEGMA or DMA with a disulfide-based dimethacrylate. The disulfide bonds were reductively cleaved using tri-Bu phosphine to generate reactive thiol groups. Thiol-ene chem. was utilized for further derivatization with thiol-based biol. important mols. and heavy metals for tissue engineering or bioimaging applications, resp.

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    Blanazs, A.; Armes, S. P.; Ryan, A. J. Self-Assembled Block Copolymer Aggregates: From Micelles to Vesicles and Their Biological Applications. Macromol. Rapid Commun. 2009, 30 (4–5), 267– 277,  DOI: 10.1002/marc.200800713

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    Self-assembled block copolymer aggregates: from micelles to vesicles and their biological applications

    Blanazs, Adam; Armes, Steven P.; Ryan, Anthony J.

    Macromolecular Rapid Communications (2009), 30 (4-5), 267-277CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)

    A review. The ability of amphiphilic block copolymers to self-assemble in selective solvents has been widely studied in academia and utilized for various com. products. The self-assembled polymer vesicle is at the forefront of this nanotechnol. revolution with seemingly endless possible uses, ranging from biomedical to nanometer-scale enzymic reactors. This review is focused on the inherent advantages in using polymer vesicles over their small mol. lipid counterparts and the potential applications in biol. for both drug delivery and synthetic cellular reactors.

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68. 68

    Le Fer, G.; Portes, D.; Goudounet, G.; Guigner, J.-M.; Garanger, E.; Lecommandoux, S. Design and Self-Assembly of PBLG- b -ELP Hybrid Diblock Copolymers Based on Synthetic and Elastin-like Polypeptides. Org. Biomol. Chem. 2017, 15 (47), 10095– 10104,  DOI: 10.1039/C7OB01945A

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    Tan, J.; Bai, Y.; Zhang, X.; Zhang, L. Room Temperature Synthesis of Poly(Poly(Ethylene Glycol) Methyl Ether Methacrylate)-Based Diblock Copolymer Nano-Objects via Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA). Polym. Chem. 2016, 7 (13), 2372– 2380,  DOI: 10.1039/C6PY00022C

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    Room temperature synthesis of poly(poly(ethylene glycol) methyl ether methacrylate)-based diblock copolymer nano-objects via Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA)

    Tan, Jianbo; Bai, Yuhao; Zhang, Xuechao; Zhang, Li

    Polymer Chemistry (2016), 7 (13), 2372-2380CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)

    The photoinitiated polymn.-induced self-assembly (photo-PISA) of 2-hydroxypropyl methacrylate (HPMA) is conducted in water by using poly(poly(ethylene glycol) Me ether methacrylate) (PPEGMA) based macro-RAFT agents. Polymns. were carried out at room temp. via exposure to visible light irradn., and quant. monomer conversions (>99%) were achieved within 30 min of visible light irradn. A remarkably diverse set of complex morphologies (spheres, worms, and vesicles) have been prepd. by aq. photo-PISA under mild conditions (water medium, room temp., and visible light). The morphol. of nano-objects can be tuned by changing the reaction parameters (e.g. d.p., solids concn.), and two detailed phase diagrams were constructed. The polymn. can be activated or deactivated by a simple "ON/OFF" switch of the light source. A thermo-responsive behavior of PPEGMA14-PHPMA200 nanoparticles prepd. at 15% wt./wt. was investigated by changing the temp. from 25 °C to 4 °C.

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70. 70

    Docherty, P. J.; Girou, C.; Derry, M. J.; Armes, S. P. Epoxy-Functional Diblock Copolymer Spheres, Worms and Vesicles via Polymerization-Induced Self-Assembly in Mineral Oil. Polym. Chem. 2020, 11 (19), 3332– 3339,  DOI: 10.1039/D0PY00380H

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    Parkinson, S.; Knox, S. T.; Bourne, R. A.; Warren, N. J. Rapid Production of Block Copolymer Nano-Objects via Continuous-Flow Ultrafast RAFT Dispersion Polymerisation. Polym. Chem. 2020, 11 (20), 3465– 3474,  DOI: 10.1039/D0PY00276C

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    Rapid production of block copolymer nano-objects via continuous-flow ultrafast RAFT dispersion polymerization

    Parkinson, Sam; Knox, Stephen T.; Bourne, Richard A.; Warren, Nicholas J.

    Polymer Chemistry (2020), 11 (20), 3465-3474CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)

    Ultrafast RAFT polymn. is exploited under dispersion polymn. conditions for the synthesis of poly(dimethylacrylamide)-b-poly(diacetoneacrylamide) (PDMAmx-b-PDAAmy) diblock copolymer nanoparticles. This process is conducted within continuous-flow reactors, which are well suited to fast reactions and can easily dissipate exotherms making the process potentially scalable. Transient kinetic profiles obtained in-line via low-field flow NMR spectroscopy (flow-NMR) confirmed the rapid rate of polymn. while still maintaining pseudo first order kinetics. Gel permeation chromatog. (GPC) reported molar mass dispersities, D < 1.3 for a series of PDMAmx-b-PDAAmy diblock copolymers (x = 46, or 113; y = 50, 75, 100, 150 and 200) confirming control over mol. wt. was maintained. Particle characterization by dynamic light scattering (DLS) and transmission electron microscopy (TEM) indicated successful prepn. of spheres and a majority worm phase at 90° but the formation of vesicular morphologies was only possible at 70°. To maintain the rapid rate of reaction at this lower temp., initiator concn. was increased which was also required to overcome the gradual ingress of oxygen into the PFA tubing which was quenching the reaction at low radical concns. Ill-defined morphologies obsd. at PDAAm DPs close to the worm-vesicle boundary, combined with a peak in molar mass dispersity suggested poor mixing prevented an efficient morphol. transition for these samples.

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    Pedersen, J. S. Form Factors of Block Copolymer Micelles with Spherical, Ellipsoidal and Cylindrical Cores. J. Appl. Crystallogr. 2000, 33 (3), 637– 640,  DOI: 10.1107/S0021889899012248

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    Form factors of block copolymer micelles with spherical, ellipsoidal and cylindrical cores

    Pedersen, Jan Skov

    Journal of Applied Crystallography (2000), 33 (3, Pt. 1), 637-640CODEN: JACGAR; ISSN:0021-8898. (Munksgaard International Publishers Ltd.)

    The form factor of a micelle model with a spherical core and Gaussian polymer chains attached to the surface has previously been calcd. anal. by Pedersen and Gerstenberg. Non-penetration of the chains into the core region was mimicked in the anal. calcns. by moving the center of mass of the chains Rg away from the surface of the core, where Rg is the radius of gyration of the chains. In the present work, the calcns. have been extended to micelles with ellipsoidal and cylindrical cores. Non-penetration was also for these taken into account by moving the center of mass of the chains Rg away from the core surface. In addn. results for worm-like micelles, disk-shape micelles and micelles with a vesicle shape are given.

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    Guinier, A.; Lorrain, P.; Lorrain, D. S.-M.; Gillis, J. X-Ray Diffraction in Crystals, Imperfect Crystals, and Amorphous Bodies. Phys. Today 1964, 17 (4), 70– 72,  DOI: 10.1063/1.3051547

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